Flexible display device

ABSTRACT

A flexible display device ( 10 ) is disclosed. The flexible display device comprises a flexible substrate ( 12 ), a number of display pixels ( 14 ) arranged in a form of rows and columns on the surface of the substrate, a number of grooves ( 16 ) in the surface of the substrate each of which is formed in between adjacent two rows or columns of the display pixels ( 14 ), and connection lines ( 18 ) for electrically interconnecting the plurality of display pixels ( 14 ), thereby providing flexibility to the display device and, at the same time, minimizing the propagation of mechanical stress caused when the display device is bent or rolled. A method of manufacturing the display device is also disclosed.

FIELD OF THE INVENTION

The present invention relates generally to a display device. Moreparticularly, the invention relates to a flexible display device, whichcan be rolled up in a preferential direction. The invention also relatesto a method of manufacturing such flexible display devices.

BACKGROUND OF THE INVENTION

In general, a display panel device consists of a substrate layer, anumber of display pixels disposed on the surface of the substrate, andpixel switching circuitry. The display pixels are arranged in a form ofplural rows and columns.

Conventionally, flexible substrates such as a plastic substrate havebeen utilized to provide a mechanical flexibility to display devices.However, there has been a limitation to the degree of flexibility sincethe flexibility of the display panel relies on only that of the plasticsubstrate. In addition, the mechanical stress caused by bending orflexing is propagated throughout the whole displaying area, particularlythe display pixels. Therefore, the display performance characteristicsof the pixels are adversely affected so that it can not work properly asa display device, especially when excessively bent or severely flexed.

Accordingly, there is a need to solve the conventional problems notedabove and to provide a novel flexible display device in which itsflexibility can be maximized and the propagation of mechanical stresscan be minimized, without damaging the display performance.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided aflexible display device. The display device comprises (a) a flexiblesubstrate; (b) a plurality of display pixels arranged in a form of rowsand columns on the surface of the substrate; (c) a plurality of firstgrooves in the surface of the substrate, the first groove being formedin between adjacent two rows or columns of the display pixels, therebyproviding flexibility to the display device and, at the same time,minimizing the propagation of mechanical stress caused when the displaydevice is bent or rolled; and (d) a plurality of connection lines forelectrically interconnecting the plurality of display pixels. Thedisplay device can further include a plurality of second grooves, eachof which is formed in between adjacent two columns or rows of thedisplay pixels thereby enhancing the flexibility of the display device,the first and second grooves being substantially perpendicular to eachother.

According to another aspect of the present invention, there is provideda flexible display device. The display device comprises (a) a flexiblesubstrate having a first and second surfaces; (b) a plurality of displaypixels arranged in a form of rows and columns on the first surface ofthe substrate; (c) a plurality of first parallel grooves in the firstsurface of the substrate, the first groove being formed in betweenadjacent two rows or columns of the display pixels, thereby providingflexibility to the display device and, at the same time, minimizing thepropagation of mechanical stress caused when the display device is bentor rolled; and (d) a plurality of connection lines for electricallyinterconnecting the plurality of display pixels. The connection linescomprise: (a) a plurality of row connection lines provided on the secondsurface of the substrate, each row connection line corresponding to eachrespective row of display pixels; (b) a plurality of column connectionlines provided on the second surface of the substrate, each columnconnection line corresponding to each respective column of displaypixels; and (c) a plurality of vertical connection lines each connectingeach display pixel on the first surface with a corresponding row orcolumn connection line on the second surface, wherein an insulationlayer is provided between the row and column connection lines.

According to one aspect of the present invention, there is provided amethod of manufacturing a flexible display device. The method comprisesthe steps of: (a) providing a flexible substrate having a first andsecond surface; (b) forming a plurality of first parallel grooves in thefirst surface of the substrate, each adjacent two parallel groovesdefining a pixel area therebetween; (c) providing a plurality of displaypixels on the pixel area such that the display pixels are arranged in apattern of rows and columns; and (d) providing a plurality of connectionlines to electrically interconnect the display pixels. The method canfurther include a step of forming a plurality of second parallel groovesin the first surface of the substrate such that the second groove issubstantially perpendicular to the first groove. The step of providing aplurality of connection line comprises steps of: (a) providing a firstconnection line to connect the first surface with the second surface ofthe substrate; and (b) providing a second connection line on the secondsurface of the substrate such that the first connection line serves toelectrically connect the display pixel on the first surface to thesecond connection line on the second surface. The step of providing afirst connection line comprises steps of: (a) forming a through-holepassing through the first and second surfaces of the substrate; and (b)carrying out metallization in the through-hole.

A further understanding of other aspects, features, and advantages ofthe present invention will be realized by reference to the followingdescription, appended drawings and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the invention will be described with reference to theaccompanying drawings, in which:

FIG. 1 illustrates a schematic sectional view of a flexible displaydevice according to the first embodiment of the present invention;

FIG. 2 shows the top view of the flexible display device of FIG. 1;

FIG. 3 is a schematic representation of a sectional view of a flexibledisplay device according to the second embodiment of the presentinvention;

FIG. 4 depicts the top view of the flexible display device of FIG. 3;

FIG. 5 is a schematic cross-sectional view taken along the line A—A inFIG. 4 with the pixel electronics omitted;

FIG. 6 is a schematic cross-sectional view taken along the line B—B inFIG. 4 with the pixel electronic omitted;

FIG. 7 illustrates a top plan view of a flexible display deviceaccording to the third embodiment of the invention;

FIGS. 8 a to 8 j sequentially illustrate a manufacturing process of theflexible display device in accordance with the fourth embodiment of theinvention; and

FIGS. 9 a to 9 r show sequential steps of a manufacturing process of theflexible display device in accordance with the fifth embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

In FIGS. 1 and 2, there is schematically illustrated a flexible displaydevice in accordance with the first embodiment of the present invention,which is generally denoted by a reference numeral 10. FIG. 1 is thecross-sectional view of the display device, and FIG. 2 illustrates thetop plan view thereof.

Referring to FIGS. 1 and 2, the flexible display device 10 comprises aflexible substrate 12 such as a plastic substrate, a plurality ofdisplay pixels 14 provided on the surface of the substrate 12, aplurality of grooves 16 formed between the display pixels 14, and aplurality of connection lines 18 for electrically interconnecting thedisplay pixels 14. In this embodiment, the display pixels 14 arearranged in a pattern of plural rows and columns as is shown in FIG. 2.The groove 16 can be formed in between any adjacent rows or columns ofthe display pixels, for example, in a regular pattern. In thisembodiment, the grooves 16 are provided in between every adjacent twocolumns of display pixels and formed substantially parallel to thecolumns. The connection lines 18 include a plural of column connectionlines 18C and a plural of row connection lines 18R, which serve toelectronically interconnect the columns and rows of display pixelsrespectively, as is illustrated in FIGS. 2. An insulation layer (notshown in FIGS. 1 and 2) is provided between the row and columnconnection lines 18R and 18C, which are substantially perpendicular toeach other.

The grooves 16 define a pixel area 13 in-between where the displaypixels 14 are placed. Accordingly, by virtue of the grooves 16, thepixel area 13 is mechanically isolated, and the whole display device 10is provided with a greater flexibility, especially to the extent that itcan be rolled up or folded. The mechanical isolation of the pixel area13 serves to minimize the stress propagation from the substrate 12 tothe pixel area 13, i.e., the display pixels 14 when rolled or bent. Thatis, the minimal influence on display performance characteristics can beachieved. Therefore, the display device 10 of the invention can bestored in a compact rolled state, for example, in a cylindrical casing,and can be flattened out when in use. Furthermore, the flexible displaydevice 10 can operate even when it remains bent or wrapped around acylindrical surface.

In the embodiment of FIGS. 1 and 2, although the display device 10 isprovided with a plural of columnar grooves 16 only, it can furtherinclude a plural of row grooves 16R as illustrated in FIG. 7. Each rowgroove 16R is provided in between each adjacent two rows of displaypixels, thereby improving the flexibility of the display device. Thecolumn and row grooves 16C, 16R are substantially perpendicular to eachother.

As illustrated in FIG. 1, the grooves 16 can take either a rectangularor rounded cross-section.

Each display pixel 14 includes an electro-luminescent display layer suchas a polymer or organic emitting diode (OLED) and pixel electronics suchas thin-film-transistor based switching circuitry. The pixel electronicscan be integrated in a stacked pixel configuration on the pixel area 13.

FIGS. 3 to 6 schematically depict a flexible display device 10 inaccordance with the second embodiment of the present invention. FIG. 3is the cross-sectional view of the display device, and FIG. 4illustrates the top plan view thereof. FIGS. 5 and 6 are cross-sectionalviews taken along the lines A—A and B—B respectively in FIG. 4.

Similar to the previous embodiment of FIGS. 1 and 2, the flexibledisplay device 10 of FIGS. 3 to 6 comprises a flexible substrate 12 suchas a plastic substrate, a plurality of display pixels 14 provided on thesurface of the substrate 12, a plurality of grooves 16 formed betweenthe display pixels 14, and a plurality of connection lines 17 and 18 forelectrically interconnecting the display pixels 14. Likewise, theconfiguration of the elements is essentially identical in bothembodiments, except for that of the connection lines.

Referring to FIGS. 3 to 6, the structure of the connection line of thisembodiment will be described hereafter in greater detail.

In this embodiment, the connection line for electrically interconnectingthe display pixels comprise a plural of row connection lines 18R, aplural of column connection lines 18C, and a plural of verticalconnection lines 17. According to this embodiment, the row and columnconnection lines 18R and 18C are provided on the opposite side to thesurface of the substrate 12 where the display pixels 14 are disposed. Aninsulation layer 19 a is provided between the row and column connectionlines 18R, 18C, as clearly illustrated in FIGS. 5 and 6. The verticalconnection line 17 serves to connect each display pixel 14, for examplea pixel contact 15 (on which the display pixel is integrated) with eachcorresponding row or column connection lines. More specifically, thevertical connection line 17 includes a column vertical connection line17C and a row vertical connection line 17R. In this embodiment, eachdisplay pixel 14 is provided with a row vertical connection line 17R anda column vertical connection line 17C, which electronically connect thedisplay pixel 14 to a corresponding row and column connection lines 18R,18C respectively, as clearly depicted in FIGS. 5 and 6. Further detailof the connection lines 17, 18 will be described hereinafter, inconjunction with manufacturing processes of the flexible display of theinvention.

In FIG. 7, there is schematically shown a top plan view of a flexibledisplay device in accordance with the third embodiment of the invention.As noted above and illustrated in FIG. 7, the display device of theinvention can be further provided with a plurality of row grooves 16Rtogether with a plurality of column grooves 16C, thereby improving theflexibility of the display device. Likewise, each row groove is formedin between each adjacent two rows of display pixels 14.

According to another embodiment of the invention, there is provided amethod of manufacturing the flexible display devices described above.The method, in general, includes a step of forming a number of parallelgrooves in the surface of a flexible substrate, such that a columnarpixel area is defined between each adjacent two grooves as illustratedin FIGS. 2 and 4. The parallel grooves can consist of a plurality ofparallel row grooves and a plurality of parallel column grooves. In thiscase, each adjacent two row grooves define an isolated pixel area incombination with each adjacent two column grooves, as shown in FIG. 7.According to the method, then, a number of display pixels are providedon the pixel area defined between the grooves such that the displaypixels are arranged in a form of parallel rows and columns, and the rowand column of pixels are parallel with the row and column groovesrespectively. The method of the invention also includes a step offorming a connection line to electronically interconnect the displaypixels, depending on the design of the display device. Details of theabove steps will be described hereinafter, in conjunction with FIGS. 8 ato 9 r.

It is noted that the order of the steps of the method, which isdescribed above and will be further described hereafter, can be switchedwith each other, depending on the design of the display, or undercertain manufacturing conditions and circumstances.

In FIGS. 8 a to 8 j, there is sequentially and schematically illustrateda method of manufacturing a flexible display device in accordance withthe fourth embodiment of the invention. The method will be explained ingreater detail hereafter.

FIGS. 8 a to 8 d show, in sequence, a process of forming a plurality ofgrooves in the surface of a flexible substrate 12. For convenience ofthe illustration and description, there is shown only two parallelgrooves 16, between which a pixel area 13 is defined. The grooves 16 canbe formed in the flexible plastic substrate 12 by using, for example, ametal (or other) masking technique and reactive ion etching (RIE)process in an atmosphere of CF₄+O₂ mixture. That is, a thin-film metal12 a is first deposited on the flexible substrate 12 and then patternedaccording to a desired outline and dimensions of the grooves as shown inFIG. 8 b. Then, the metal-patterned substrate is transferred into a RIEchamber, where the area of the substrate surface which is free from themetal 12 a is etched and eventually results in the grooves 16 asdepicted in FIG. 8 c. After RIE-etching of the substrate, the metal mask12 a is removed by using a wet etchant, or the like as shown in FIG. 8d. Alternatively, the grooves in the plastic substrate can be formed bymeans of a laser micromachining process or a projection lasermicromachining process, which are well-known in the art.

Depending on the requirements of pixel size and the desired degree ofbending (radius of curvature), the depth and width of the grooves can becontrolled during the above processes such that the mechanical integrityof the substrate can be maintained while minimizing the influence ondisplay performance characteristics.

FIGS. 8 e to 8 j sequentially illustrate the step of providing a displaypixel 14 and a connection line 18 between adjacent pixels. As well-knownin the art, the display pixel 14 associates various pixel electronics,including conducting layers, several dielectric layers 11 a, 11 c and 11d, and can electrode 11 b, a source and drain metal 11 f, an OLED(Organic Light Emitting Diode) cathode 11 e, an organic layer 11 g, orthe like. Although an OLED device is illustrated as a display pixel,various other types of pixel devices can be integrated together withother necessary components. The above display pixel and relatedcomponents, and the connection line 18 can be formed by means of variousconventional semiconductor processes such as lithography or the like.

In FIGS. 9 a to 9 r, there is sequentially and schematically illustrateda method of manufacturing a flexible display device in accordance withthe fifth embodiment of the invention. The method will be explained ingreater detail, referring to the flexible display device shown in FIGS.3 to 6.

In this embodiment, the step of forming a connection line between thedisplay pixels is different from that of the previous one. Other stepsare essentially identical with those of the previous embodiment. Thatis, the step of forming the connection lines includes steps of providinga first connection line perforating a flexible substrate, and providinga second connection line on the opposite side to the surface of thesubstrate where the display pixels are placed, such that the firstconnection line serves to electrically connects the display pixel on thesurface to the second connection line. In the figures, the firstconnection line is denoted by reference numerals 17C or 17R, and thesecond connection line by 18C or 18R. The first connection lines 17C,17R correspond to the vertical connection lines 17C, 17R in FIGS. 3 to6.

According to this embodiment of the invention, the step of providing afirst connection line comprises steps of forming a through-hole passingthrough the substrate, and carrying out metallization in thethrough-hole.

FIGS. 9 a to 9 f show the forming procedures of a first connection line17C or 17R. As illustrated in FIGS. 9 a to 9 d, the step of making athrough-hole 11 is similar to the groove forming process described abovein conjunction with FIGS. 8 a to 8 d. That is, a metal masking andpatterning process and a reactive ion etching (RIE) process, a lasermicromachining process, or a projection laser micromachining process canbe utilized, which are well-known processes in the art. A metal layer 12b such as an Al layer is provided on the opposite side to the substratesurface where the metal masking 12 a is deposited. The metal layer 12 bis used for providing the second connection lines 18C and 18R insubsequent steps of the method.

FIGS. 9 e and 9 f schematically illustrate the step of metallizing thethrough-holes 11 to forming the first connection lines 17C and 17R.Various conventional processes can be used for metallization of thethrough-holes 11, including an electro- or electroless depositionprocess.

In FIGS. 9 g to 9 l, there is schematically depicted the step ofproviding the second connection lines 18C and 18R. Specifically, asshown in FIG. 9 h, by patterning the metal layer 12 b, a secondconnection line 18C is formed, which corresponds to the columnconnection line in FIGS. 4 to 6. Then, a first insulation layer 19 asuch as a dielectric layer is deposited over the second connection line18C. As illustrated in FIGS. 9 j to 9 l, opening vias in the insulationlayer 19 a, and deposition and patterning another metal layer arecarried out to provide another second connection line 18R, whichcorresponds to the row connection line in FIGS. 4 to 6. Then anotherinsulation layer 19 b such as a dielectric encapsulation layer isprovided above the second connection line 18R, as shown in FIG. 9 l.

Subsequently, as shown in FIG. 9 m, the grooves 16 are formed by meansof the same processes noted above, in conjunction with the previousembodiment of FIGS. 8 a to 8 j. The grooves 16 define a pixel area 13.

Similar to FIGS. 8 e to 8 j, FIGS. 9 n to 9 r schematically andsequentially illustrate the step of providing a display pixel 14. Aswell-known in the art, the display pixel 14 associates various pixelelectronics, including conducting layers, several dielectric layers, aelectrode, a source and drain metal, an OLED cathode, an organic layer,or the like. Although an OLED device is illustrated as a display pixel,various other types of pixel devices can be applied to the presentinvention. The above display pixel and related components can be formedby means of various conventional semiconductor processes such aslithography or the like.

While this invention has been described with reference to severalspecific embodiments, the description is illustrative of the inventionand is not to be construed as limiting the invention. Variousmodifications and variations may occur to those skilled in the artwithout departing from the true spirit and scope of the invention asdefined by the appended claims.

1. A flexible display device comprising: (a) a flexible substrate havinga first and second surfaces; (b) a plurality of display pixels arrangedin a form of rows and columns on the first surface of the substrate; (c)a plurality of first parallel grooves in the first surface of thesubstrate, the first groove being formed in between adjacent two rows orcolumns of the display pixels, thereby providing flexibility to thedisplay device and, at the same time, minimizing the propagation ofmechanical stress caused when the display device is bent or rolled; and(d) a plurality of connection lines for electrically interconnecting theplurality of display pixels wherein part of the connection lines isprovided on the second surface of the substrate.
 2. A flexible displaydevice according to claim 1, further comprising a plurality of secondparallel grooves, each of which is formed in between adjacent twocolumns or rows of the display pixels thereby enhancing the flexibilityof the display device, the first and second grooves being substantiallyperpendicular to each other.
 3. A flexible display device according toclaim 1, wherein each first groove is provided in between each adjacentrows or columns of the display pixels.
 4. A flexible display deviceaccording to claim 1, wherein the connection lines comprise: (a) aplurality of row connection lines provided on the second surface of thesubstrate, each row connection line corresponding to each respective rowof display pixels; (b) a plurality of column connection lines providedon the second surface of the substrate, each column connection linecorresponding to each respective column of display pixels; and (c) aplurality of vertical connection lines each connecting each displaypixel on the first surface with a corresponding row or column connectionline on the second surface, wherein an insulation layer is providedbetween the row and column connection lines.
 5. A flexible displaydevice according to claim 4, wherein the vertical connection lineincludes a column vertical connection line and a row vertical connectionline, which connect a display pixel to a corresponding column and rowconnection lines respectively.
 6. A flexible display device according toclaim 4, wherein each display pixel is provided with a column verticalconnection line and a row vertical connection line, which connect thedisplay pixel to a corresponding column and row connection linerespectively.
 7. A method of manufacturing a flexible display device,the method comprising the steps of: (a) providing a flexible substratehaving a first and second surface; (b) forming a plurality of firstparallel grooves in the first surface of the substrate, each adjacenttwo parallel grooves defining a pixel area therebetween; (c) providing aplurality of display pixels on the pixel area such that the displaypixels are arranged in a pattern of rows and columns; and (d) providinga plurality of connection lines to electrically interconnect the displaypixels comprising: (i) providing a first connection line to connect thefirst surface with the second surface of the substrate; and (ii)providing a second connection line on the second surface of thesubstrate such that the first connection line serves to electricallyconnects the display pixel on the first surface to the second connectionline on the second surface.
 8. A method according to claim 7, furthercomprising a step of forming a plurality of second parallel grooves inthe first surface of the substrate such that the second groove issubstantially perpendicular to the first groove.
 9. A method accordingto claim 7, wherein, in the step of forming a plurality of firstparallel grooves, the grooves are formed by means of a metal masking andpatterning process and a reactive ion etching (RIE) process.
 10. Amethod according to claim 7, wherein, in the step of forming a pluralityof first parallel grooves, the grooves are formed by means of a lasermicromachining process or a projection laser micromachining process. 11.A method according to claim 7, wherein the step of providing a firstconnection line comprises steps of: (a) forming a through-hole passingthrough the first and second surfaces of the substrate; and (b) carryingout metallization in the through-hole.